Originally meaning "Player Killing," the term PK is now also colloquially used in China and Taiwan as a verb form of the word versus in situations where there may actually be no avatar/player killing. It is most used in 1v1 situations like 1v1 basketball, 1v1 starcraft, 1v1 league of legends, 1v1 chess, 1v1 eating contests, 1v1 footrace etc. PK can also be applied to situations where one team is against another in a 1 team vs 1 team scenario like in the NBA, soccer, baseball, etc.

not to be confused with Penis Kissing unless you want to piss off Asians.

FOB: Robert and Ted are playing basketball tonight. Let's go watch them PK.
nonFOB: Don't use the term PK. People may think you're referring to Penis Kissing (touching the tip of a dick with another).
FOB: Shut up.